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 Do Spark Plugs Wear Out?

 Created by: Rosebud
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 Posted: Jul 1, 2020 07:00AM
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CA
Quote:
Originally Posted by croc7
The replacement interval cited in the Haynes 'regular maintenance' section is 12 months/12,000 miles.  But who knows the source for that information?  Probably taken from a shop manual written in the '60's.
Yes, plug electrodes don't seem to erode the way they did back then. Could have been the leaded fuel used or lower compression. slower rpms allowing the plug electrodes to heat up, or the alloy of the electrodes themselves. We'd also see cracked porcelain on the inner electrode, usually from it overheating and cracking the porcelain. Points seemed to wear more aggressively then too - metal transfer from one point face to the other resulting in a sharp tooth forming on one and a corresponding cavity in the other.

.

"Hang on a minute lads....I've got a great idea."

 Posted: Jun 30, 2020 11:49AM
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The replacement interval cited in the Haynes 'regular maintenance' section is 12 months/12,000 miles.  But who knows the source for that information?  Probably taken from a shop manual written in the '60's.  Technology and materials must have improved that would allow a longer interval between change.  Since the early 70's, in cars from a Z28 to a BMW 2002 tii to a 1275 Cooper S to a SAAB Turbo, I had one spark plug fail.  One.  Having said that, I clean and check the gap on mine every six months.  Probably do more harm than good to the sealing gasket but spark plugs are cheap from Rock Auto. 

 

"To catch one, you need one"....John Cooper

 Posted: Jun 30, 2020 09:37AM
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Quote:
Originally Posted by CooperTune
Over what period of time did you drive this 10,000 miles? What plugs are you using?
The plugs were NGK BP7ES and were about 5 years old. I checked them frequently. They were always a nice, light chocolate brown color—no sign of fouling.

 

Michael, Santa Barbara, CA

. . . the sled, not the flower

      Poser MotorSports

 Posted: Jun 30, 2020 09:24AM
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Over what period of time did you drive this 10,000 miles? What plugs are you using?
It's nice when a simple plug change solves a starting issue. I recently parked one for
fouling out #1 plug every four days. Dead miss, thinking rings or guides. Steve (CTR)

 Posted: Jun 30, 2020 08:41AM
 Edited:  Jun 30, 2020 09:01AM
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Other than obvious visible wear to the electrodes, do spark plugs wear out internally? Over the last few weeks my otherwise easy-starting motor began taking 4 to 5 seconds of cranking before it would fire up. Once started it ran fine. The other day it refused to fire.

Fuel supply seemed fine, 2 to 3 psi on the gauge and the plugs were wet, because of course, I flooded it trying to get it started. I pulled a couple of plugs and got a visible spark on each. The plugs had about 10K miles on them but otherwise looked fine. I know that's pushing things a bit, but as I said, it ran well. Out of ideas I decided to change the plugs because, well, they were (over)due. To my surprise, the engine started right up and has continued to do so. Other than jiggling some wires around under the bonnet in my search for the problem, I have no explanation other than worn-out plugs. Is this possible?

 

Michael, Santa Barbara, CA

. . . the sled, not the flower

      Poser MotorSports